Exogenous genes can be stably introduced into the mammalian cell chromosome by DNA-mediated gene transfer (transformation). The proposed research employs transformation as a bioassay for the functional roles of specific DNA sequences in gene expression and regulation. A sequence element required for transcription of the Herpes Virus thymidine kinase (tk) gene has been identified, and its function will be further defined by generating in vitro a systematic series of tk mutants and assaying their function upon transfer into mammalian cells in culture. Another set of experiments is aimed at defining the regions of a cloned Drosophila heat shock gene, hsp-70, which are responsible for its increased expression upon heat treatment. We have found that this wild-type dipteran gene can be introduced into murine cells where it can be correctly transcribed in response to heat shock treatment of the mouse cells. Chimeric genes containing selected portions of the Drosophila hsp-70 gene will be constructed by molecular cloning and assayed for heat-induced expression in mammalian cells to discern which regions of the Drosophila gene are essential for induction. Finally, cloned human globin genes have been introduced into mouse erythroleukemia cells, and experiments are described to study their expression and regulation when the cells are induced to undergo erythroid maturation events.